Animate turrets Shooting
The simplest solution would be to create an animation that can be looped.

The most "proper" way to do this is with the Action Editor and Dope Sheet, but I don't understand it well. Someone else might provide that info.

However, you can also use the Graph Editor. If you create an empty that you can animate and slave the turret to that (parent, track to, child of, copy location, vertex parent, lots of options there), you can animate one "vibration" of the turret and then just repeat that same action a number of times. To do that, select the channel that you want to repeat (you might have to do this with each channel), press n, click Add Modifier and choose Cycles. To make it vibrate on demand, instead of constantly, animate the Influence value. Turn Influence to 0.0 when you want it to stop, and then bring it back up to 1.0 when you want a burst of fire.

Note: You don't necessarily have to use an empty, you could just animate the turret, but using an empty lets you isolate the curves for that one animation from other animations you might want to do. I.e. you only add modifiers to the empty's curves, without affecting other animations that you do to the acutal turrets.

Hope that helps!